This project is comprised of research into the structure and functioning of ion transport systems. There are currently 3 subprojects. 1) Research into the topology of the catalytic subunit of the Na,K-ATPase. 2) A study of the regulation and expression of the Na,K-ATPase isoforms. These two subjects utilize site-directed antibodies raised against synthetic peptides as structural probes. 3) A study of the transient kinetics of the sodium pump The conformational changes that accompany the phosphorylation and dephosphorylation of the catalytic site of are under investigation. This subproject utilizes a rapid-quenching device for the study of phosphorylation reactions in the millisecond time range.